On-Demand Optical Generation of Single Flux Quanta

Abstract

Superconductors can host quantized magnetic flux tubes surrounded by supercurrents, called Abrikosov vortices. Vortex penetration into a superconducting film is usually limited to its edges and triggered by external magnetic fields or local electrical currents. With a view to novel research directions in quantum computation, the possibility to generate and control single flux quanta in situ is thus challenging. We introduce a far-field optical method to sculpt the magnetic flux or generate permanent single vortices at any desired position in a superconductor. It is based on a fast quench following the absorption of a tightly focused laser pulse that locally heats the superconductor above its critical temperature. We achieve ex-nihilo creation of a single vortex pinned at the center of the hotspot, while its counterpart opposite flux is trapped tens of micrometers away at its boundaries. Our method paves the way to optical operation of Josephson transport with single flux quanta.

Toward the Light‐Operated Superconducting Devices: Circularly Polarized Radiation Manipulates the Current‐Carrying States in Superconducting Rings

“…Below we consider a temperature quench [ 35–39 ] of the ring from normal to superconducting state under static magnetic field $$\Phi =-\Phi _{0}/2$$. In the absence of radiation, KZM provides an equal probability of realization of these states (≈50%, since the activated energy of all other states is much larger).…”

“…To minimize the heating effect induced by the radiation, it will be advantageous to use a sapphire substrates that have high thermal conductivity 10 3 W mK −1 [45] and can provide a very efficient thermal bath to achieve sub-ns quenching times. [35,36,39] For E L ∕𝜔 L ≈ 0.75, the radiation intensity needed for optimal switching condition is ≈ 3 mW cm −2 . In this case the temperature rise of the superconducting ring on a sapphire substrate of 1 μm thickness will not exceed 3 × 10 −2 K and can therefore be safely neglected.…”

“…To minimize the heating effect induced by the radiation, it will be advantageous to use a sapphire substrates that have high thermal conductivity 10 3 $$\mathrm{W \nobreakspace mK}$$ −1 [ 45 ] and can provide a very efficient thermal bath to achieve sub‐ns quenching times. [ 35,36,39 ] For $$E_{\text{L}}/\omega _{\text{L}}\approx 0.75$$, the radiation intensity needed for optimal switching condition is $$\approx 3\nobreakspace \text{m}\mathrm{W \nobreakspace }\text{c} \mathrm{m}^{-2}$$. In this case the temperature rise of the superconducting ring on a sapphire substrate of $$1\ \umu \mathrm{m}$$ thickness will not exceed $$3\times 10^{-2}\ \mathrm{K}$$ and can therefore be safely neglected.…”

“…However, if we combine the KZM with IFE induced by a circular polarized radiation we can effectively discriminate/distinguish between states with different current polarity. [25] Below we consider a temperature quench [35][36][37][38][39] of the ring from normal to superconducting state under static magnetic field Φ = −Φ 0 ∕2. In the absence of radiation, KZM provides an equal probability of realization of these states (≈50%, since the activated energy of all other states is much larger).…”

All-optical generation of Abrikosov vortices by the Inverse Faraday Effect

“…In order to generate the vortex with a desired polarity at a desired position, one can use a focused laser pulse, which initiates the local rapid quench of the superconductor in the presence of a weak magnetic field (see Ref. [23]). The combined effect of the thermal force f T ∼ −∇T and the Lorentz force arising from Meissner currents f L ∼ j M is able to separate vortex-antivortex pairs formed after quench with further transfer of desired polarity at the position of the laser spot and expelling the opposite fluxes to the edges of the superconductor.…”